1. Field of the Invention
The present invention relates to an image processing device for detecting the movement of an image by measuring the movement vector of the image and, more particularly, the present invention relates to a pretreatment device to recognize the moving images.
2. Related Background Art
In this field, there are already known two methods for detecting the movement vector, namely a gradient method and a matching method. The gradient method is described in Japanese Patent Publication No. 60-46878, and in the article "Measuring the speed of moving objects from Television Signals", IEEE. Trans. Com., Com-23,4 pp.474-478 (April 1975), written by J. O. Limb and J. A. Murphy, etc. The matching method is also explained, for example, in the literature, entitled as "A device for detecting the moving vector for muse application", in the Television Academic Institute's Technical Report PP OE59-5, written by Uichi Ninomiya, etc.
There is a close co-relation between the pattern size of an object shown in the image, namely its space frequency, and the detection accuracy for a movement vector to be detected from the image. For example, when case an image of high spatial frequency, which includes periodic patterns such as stripe pattern, is to be detected, the gradient method tends to narrow the range of its detection while the matching method tends to increase the probability for erroneous detection. When an image of low spatial frequency such as an image showing a plain wall without a pattern is in full picture, both methods cause erroneous detection.
Furthermore, since both detection methods are designed to handle a multivalued density gradation, they have the common problem of equipment with complicated hardware components. On the other hand, the pattern matching of a binary image enables the simplification of the hardware components but it causes its sensor to detect different patterns when under lighting having different values of brightness thus resulting in a drawback that is likely to produce erroneous detection.